Presentation on theme: "Chemical Reactions. Chemical Equations A chemical equation is a representation of a chemical reaction; the formulas of the reactants (on the left) are."— Presentation transcript:
Chemical Equations A chemical equation is a representation of a chemical reaction; the formulas of the reactants (on the left) are connected by an arrow with the formulas of the products (on the right). Fe + O 2 Fe 2 O 3 A Chemical formula is a combination of symbols that represent the elements in a compound. (add this note to your reading guide )
All chemical reactions have two parts Reactants - the substances you start with (the ones reacting) Products- the substances you end up with (the ones produced) The reactants turn into the products. Reactants Products
A chemical reaction rearranges the atoms of the reactants to form new compounds of the products. No new atoms are created, they have only been rearranged.
4 types of Chemical Reactions: 1.Synthesis Reaction: two or more elements or compounds combine to make one more complex substance (A + B → AB) 1.Decomposition Reaction: a compound is broken down into simpler products (AB → A + B) 2.Single Replacement Reactions: replace one element from a compound with another element. (A + BC B + AC) 4. Double Replacement Reactions: swaps elements between 2 compounds that react together to form two new compounds. (AB + CD AD + CB)
The Law of Conservation of Mass states that: The mass of the reactants equals the mass of the products. OR - Matter can never be created nor destroyed OR - you can’t get somethin’ outta nothin’(hahaha)
Word Equations Example Methane + Oxygen Carbon dioxide + Water The arrow means yields, gives, or reacts to produce.
Rules for balancing Write the correct formulas for all the reactants and products Count the number of atoms of each type appearing on both sides Balance the elements one at a time by adding coefficients (the numbers in front) Check to make sure it is balanced.
Never Change a subscript to balance an equation. If you change the formula you are describing a different reaction. H 2 O is a different compound than H 2 O 2 Never put a coefficient in the middle of a formula 2 NaCl is okay, Na2Cl is not.
What is a coefficient? A number that indicates how many atoms of an element are in one molecule What is a subscript? Numbers telling how many molecules are involved in a chemical reaction